Mutations in CSRP3/MLP, a Z-disc associated gene are functionally associated with dilated cardiomyopathy in Indian population

CSRP3 is a LIM domain containing protein, known to play an important role in cardiomyocyte development, differentiation and pathology. Mutations in CSRP3 gene are reported in both dilated and hypertrophic cardiomyopathy (DCM and HCM), however, the genotype-phenotype correlation still remains elusive. To investigate the pathogenic potential of CSRP3 variants in our DCM cohort, we have screened 100 DCM cases and 100 controls and identified 3 non-synonymous variations, of which two are missense variants viz., c.233 GGC>GTC, p.G78V; c.420 TGG>TGC, p.W140C, and the third one is a single nucleotide polymorphism (SNP) c.46 ACC>TCC, p.T16S. These variants were absent from 100 control individuals (200 chromosomes). In vitro functional analysis has revealed reduction of CSRP3 protein level in stably-transfected C2C12 cells with p.G78V or p.W140C variants. Immunostaining demonstrates both cytoplasmic and nuclear localization of the wild-type protein, however variants p.G78V and p.W140C cause obvious reduction in the cytoplasmic expression of CSRP3 protein which is more pronounced in case of p.W140C. Disarrayed actin cytoskeleton was also observed in mutants. Besides, the expression of target genes namely Ldb3, Myoz2, Tcap, Tnni3 and Ttn are also downregulated in response to these variants. GST-pulldown assay has also showed a diminished binding of CSRP3 protein with -Actinin due to both variants p.G78V and p.W140C. Both 2D, 3D-modeling have shown confirmational changes. Most in silico tools predict these variants as deleterious. Taken together, all these results suggest the impaired gene function due to these deleterious variants in CSRP3, implicating its possible disease causing role in DCM.